1. Field of the Invention
The present invention relates to a valve timing control device.
2. Description of the Prior Art
A typical valve timing control device is described, for example, in Japanese Examined Patent Publication Hei Number 5(1993)-77843. In this device, helical splines are formed both in the timing pulley-side member serving as a power input member and in the camshaft-side member serving as the power output member and having, on its axis, a cam for opening and closing a valve. In addition, a piston provided with inner and outer circumferential helical splines for engaging the respective angular splines of the two members transmits power from the timing pulley-side member to the camshaft-side member.
Thus, the above device requires that helical splines be formed in four locations and, in particular, requires that helical splines differing in phase, angle or direction sometimes be formed on the inner and outer circumferences thereof, resulting in a highly complex process for manufacturing this device.